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WITec GmbH, Lise-Meitner-Str. 6, 89081 Ulm, Germany
phone +49 (0) 731 140 700, fax +49 (0) 731 140 70 200
info@WITec.de, www.WITec.de

Correlative Raman Imaging:
Geoscience Applications

Confocal Raman microscopy is a ​powerful method for high-resolution,
non-destructive and label-free
analysis of geological samples. It canidentify the chemical components andvisualize their distribution in 2D or 3D.

application noteLise-Meitner-Str. 6 • D-89081 Ulm, Germany
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The Raman principle

The Raman effect is based on the inelastic
scattering of light by the molecules ofgaseous, liquid or solid materials. Theinteraction of a molecule with photons
causes vibrations of its chemical bonds,
leading to specific energy shifts in the
scattered light. Thus, any given chemicalcompound produces a particular Raman
spectrum when excited and can be easily
identified by this individual “fingerprint.”
Raman spectroscopy is a well-established,label-free and non-destructive method foranalyzing the molecular composition of asample.

No need for compromises

Raman imaging

In Raman imaging, a confocal microscopeis combined with a spectrometer anda Raman spectrum is recorded at every
image pixel. The resulting Raman image
visualizes the distribution of the sample’s
compounds. Due to the high confocality of
WITec Raman systems, volume scans and3D images can also be generated.

The Raman effect is extremely weak, so
every Raman photon is important for
imaging. Therefore WITec Raman imaging
systems combine an exceptionallysensitive confocal microscope with anultra-high throughput spectrometer(UHTS). Precise adjustment of all opticaland mechanical elements guarantees thehighest resolution, outstanding speed andextraordinary sensitivity - simultaneously!
This optimization allows the detectionof Raman signals of even weak Raman
scatterers and extremely low material
concentrations or volumes with thelowest excitation energy levels. This isan unrivaled advantage of WITec systems.

Resolution

Lateral resolution is physicallylimited to ~200 nm, dependingon the wavelength of theincident light.

Speed

The more sensitive a system is, the shorter
the acquisition time for a single spectrum.
WITec’s Ultrafast Raman Imaging reduces
acquisition times for single Raman spectra
down to well below 1 ms.

Sensitivity

A high confocality increases the signal-to-noise ratio by reducing
the background. With the UHTS Series, WITec developed lens-based,
wavelength-optimized spectrometers with a spectral resolution
down to 0.1 cm-1 relative wavenumbers.

application noteLise-Meitner-Str. 6 • D-89081 Ulm, Germany
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Confocal Raman imaging

Large area Raman analysis: overview and details

Raman spectroscopy has long been
applied in geoscience, for example forthe identification and characterization ofminerals, or in the observation of mineralphase transitions in high and ultra-highpressure/temperature experiments. In
most cases, measurements have been
carried out with a micro-Raman setup, i.e.
information was obtained from single ormultiple points of interest on a sample.
This approach yields only limited information about the spatial distribution ofcomponents, mineral phases and chemicalvariations. However, a more detailed representation of the sample‘s chemical composition is valuable for many geologicalstudies, particularly for complex samples.
By means of confocal Raman imaging, thespatial distribution of chemical character­istics can be evaluated on different lengthscales – from large-area scans on thecentimeter scale to detailed investigations
with sub-micron resolution. WITec confocal
Raman microscopes of the alpha300 series
allow for such measurements with very
high sensitivity and resolution. Raman
imaging is a tool that provides information complementary to data obtainedby e.g. electron microprobe (EMP),
energy dispersive X-ray analysis (EDX) or
secondary ion mass spectrometry (SIMS).
These techniques acquire quantitative,
semi-quantitative elemental and isotopic
data. In addition, confocal Raman imaging
contributes the distribution of chemicalcomponents over a defined sample area.
Furthermore, considering that mostgeo-materials are to some degree transparent for near-ultraviolet (NUV), visible andnear-infrared (NIR) light, this information
can be obtained three dimensionally due
to the confocal setup of the microscopes.
The following examples highlight somekey analytical features of this techniquefor geoscience applications.

A sample from the deep biosphere of Äspö,Sweden, was studied using the large-areascan mode of a confocal Raman micros­cope (WITec GmbH), aiming to character­ize secondary cleavage fillings in a 1.8 to 1.4
billion-years-old diorite.
A section (Fig. 1A) was obtained from a drill
core from borehole KJ 0052 F01, run by SKB(Swedish nuclear fuel and waste management) and drilled from a tunnel at ~450 m
below the surface with a sampling depth
in the core of 12 m. A large-area scan of
8 x 2 mm2 was performed on this polishedsection with 800 x 200 pixels and an integration time of 36 ms per spectrum using
a 532 nm excitation wavelength.

A

B

Al

C

Si

D

Ca

E

F

G

CalciteOrganics
Fluorite
QuartzAnorthite
Titanite
Fluorapatite

Figure 1: Large area EMP and Raman analysis of a diorite sample.

(A) Overview of the polished rock section. The red rectangle indicates the analyzed sample area.
(B - D) EMP maps showing the elemental distribution for Al (B), Si (C) and Ca (D). (E) Raman image ofthe same region (integrated intensity from 140 to 300 cm-1). (F) Combined false-color Raman image ofthe same area. The colors correspond to the Raman spectra in (G). (G) Corresponding Raman spectra.
Scale bars 1 mm.
Sample courtesy of C. Heim and V. Thiel, EMP data courtesy of A. Kronz, Geobiology Group, University
of Göttingen, Germany.

application noteLise-Meitner-Str. 6 • D-89081 Ulm, Germany
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www.witec.de • info@witec.deComparing EMP maps of aluminum (Al),silicon (Si) and calcium (Ca) with Raman
images of the same area indicated a simi­
lar overall chemical contrast (Fig. 1B-F). The
color-coded Raman image and corresponding spectra (Fig. 1F, G) revealed the spatial
distribution of several mineral phases andwere in accordance with the EMP maps. Al
was mainly present in the region identified
as anorthite, an Al-rich silicate (Fig. 1B, F, G).
Accordingly, this phase was also visible in
the EMP map of Si (Fig. 1C). Another Si-richarea was identified as quartz (Fig. 1C, F, G)
by its Raman spectrum. The Ca-rich regions (Fig. 1D) were identified as titanite,
fluorite and calcite (Fig. 1F, G).
In addition to the mineral phases, organic
components were identified and locatedin the sample. The organic material (redin Fig. 1F, G) was present in a narrow layer
between two generations of hydrothermal
precipitates (fluorite and calcite, cyan andyellow in Fig. 1F, G), indicating at whichtime a “deep biosphere” was active withinthese rocks.
More detailed analysis of the data set
using the WITec Project software package
revealed further information about themineral phases (Fig. 2). Within the anor­
thite phase, two distinct spectra could be
distinguished, corresponding to different
configurations (Fig. 2A, B). In the quartz
phase, four regions were identified basedon variations in the relative peak intensities (Fig. 2D). Note the discrete edgesaround the anorthite phase. In the titanite
phase, anatase and quartz were present
as well as titanite in two distinguishable
orientations (Fig. 2E).

A

B

anorthite phase

Dquartz phaseEtitanite phase

C

Titanite
AnataseQuartzTitanite

Figure 2: Variations in different phases of the diorite sample.

(A, B) The anorthite phase: Two distinct spectra (A) with different spatial distribution within theanorthite phase (B). Scale bar in (B) 1 mm. (C) Regions containing quartz (green phase, grey rectangle)
and titanite (blue phase, red rectangle) are marked in the combined Raman image (see also Fig. 1F, G)
and further analyzed (D, E). Scale bar in (C) 1 mm. (D) The quartz phase: Distinct regions show variations of relative peak intensities in the Raman spectra. Note the edges around the anorthite phase.
Scale bar 600 µm. (E) The titanite phase contains anatase, quartz and two distinguishable titaniteorientations. Scale bar 300 µm.
Sample courtesy of C. Heim and V. Thiel, EMP data courtesy of A. Kronz, Geobiology Group, University
of Göttingen, Germany.

application noteLise-Meitner-Str. 6 • D-89081 Ulm, Germany
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Raman imaging with high spectral and spatial resolution
High spectral and spatial resolution isnecessary for observing chemical variations when they occur in micron-sizedfeatures. The spectral resolution is required
to distinguish minor compositional changes, and the spatial resolution enables the
depiction of such changes at the required
sub-micron level. This is illustrated bysmall carbonate struc­tures, so-called
globules, from the martian meteorite
ALH84001 and a terrestrial analogue
from Svalbard (mantle peridotite xenolithfrom the Bockfjorden volcanic complex,
BVC) (see Steele et al., 2007 for further
description). Fig. 3 shows the results ofconfocal Raman imaging studies of the
carbonate composition in the ALH84001
and the BVC xenoliths under­taken with aRaman microscope offering high spatialand spectral resolution. The two images inFig. 3A show the overall carbonate distribution (relative intensity integrated overthe peaks around 1090 cm-1). The spectra
showing the peak positions are depicted
in Fig. 3B. The images in Fig. 3C represent
shifts of the carbonate peak at about
330 cm-1 and clearly show discrete zones
of chemical variation on the sub-micronscale. The letters a, b, c, d represent distinct
chemical zones in the carbonate globule

A

ALH84001

BVC

B

C

ALH84001

BVC

c

b
a

d

1

2

Figure 3: Carbonate composition in ALH84001
and BVC xenoliths.

(A) Carbonate distribution. Raman intensity
integrated over the peak at ~1090 cm-1. (B)Center distribution of the carbonate signal forthe images in (A). ALH84001 in red, BVC in blue.
The letters a, b, c, d and numbers 1, 2 represent
distinct chemical zones in the carbonates (seeC). (C) Peak center shift of the carbonate peak at~330 cm-1 (light color = higher wavenumber). (D)Spectra corresponding to the images in (C).
Scale bars 20 µm.
Images are a courtesy of Meteoritics and Planetary Sciences; from Steele et al., 2007.

Dof the martian meteo­rite, the numbers 1
and 2 show zoning in the BVC carbonates.
Various carbonate reference samples
were measured to demonstrate chemicalvariation, including calcite (Ca), siderite(Si) and magnesite (Ma) (Fig. 3D). The
conclusions drawn from these observations contribute further to understanding
the processing of volatile and biologically
relevant compounds (CO2 and H2O) on
Mars and illustrate the importance of highspectral and spatial resolution in confocal
Raman microscopy studies (for a detailed
discussion see Steele et al., 2007).

application noteLise-Meitner-Str. 6 • D-89081 Ulm, Germany
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Raman imaging with high sensitivity: Revealing hidden details
Valuable compositional and structural
information may be contained even in
the smallest sample volumes. In orderto un­cover such information and resolve
chemical features, the highest possible sensitivity is required in addition to
exceptional spectral and spatial resolution.
Confocal Raman microscopes of the WITecalpha300 series provide this level of sensitivity, as all parts are optimized for achieving the highest possible throughput of
Raman-shifted photons from the sample
to the detector. This allows for the analysis
of very small and delicate samples without
the risk of damaging them. In geosciences,such materials can, for example, be aerosols or interstellar dust particles (IDPs).

A

C

Fig. 4 shows confocal Raman images of an
IDP (for further detail see Toporski et al.,2004). The video image gives an overview
of the particle (Fig. 4A). The combined
false-color Raman image (Fig. 4B) showsthat distinct regions for the components
shown in Figures 4C, D and E can be separated from each other. Further unidentified
mineral phases (Fig. 4C) are separated
from hematite/carbon-bearing phases(Fig. 4D) and hematite phases (Fig. 4E) andcould be associated with distinct regions
on the sample. The corresponding Raman
spectra are shown in Figure 4F.

High sensitivity is a prerequisite fordifferentiating labile components while
avoiding sample alteration due to exces­
sive excitation laser energy. This has also
been demonstrated on particles returned
from comet 81P/Wild2 by the NASA
Stardust spacecraft (Rotundi et al., 2008).
The study of small, delicate and unstablesamples further benefits from Raman
imaging being non-destructive, so thatsamples can subsequently be investigatedusing invasive micro-analytical techniques(e.g. SIMS, ToFSIMS, TEM, etc.) for obtaining
complementary information.

F
(D)

(E)

D
(C)

B
E

Figure 4: Raman analysis of an IDP.

(A) Video image of the IDP. (B) Combined false-color Raman image of (C - E). Colors as indicated in the spectra in (F). (C) Relative intensity distribution resulting from integration over the two peaks around 200 - 300 cm-1 (blue spectrum in F). (D) Relative intensity map of combined hematite / carbon D band
phases (1280 - 1400 cm-1, red spectrum in F). (E) Relative intensity map of hematite phases (peak at ca. 1600 cm-1, green spectrum in F). (F) Corresponding
Raman spectra. All scale bars 5 µm.

application noteLise-Meitner-Str. 6 • D-89081 Ulm, Germany
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3D Raman imaging: Unveil the information trapped inside
2D Raman microscopy visualizes the
distribution of chemical compounds on
the sample surface or (for transparent
samples) in a focal plane below thesur­face (x-y plane). 3D Raman imaging
enables more complex chemical analysesof the components‘ distribution in thesample volume (x, y and z). This is particularly advantageous for investigating bulky
geological specimens, complex emulsions
or mixtures, and living organisms.
In order to create 3D images, 2D Raman
maps are acquired in different focal planes
by automatically scanning through thesample along the z-axis. After data acquisition and processing, a 3D Raman image is
generated from the image stack.

A

Fluid inclusions were discovered in ultra-­high pressure (diamond-grade) garnets
from the Kokchetav Massif in northern
Kazakhstan (samples and data courtesyof Andrey Korsakov, Siberian Branch of theRussian Academy of Science, Novosibirsk,
Russia). Characterization of the inclusion‘schemical composition and petrographic
context may provide information on
micro-thermometry. Due to confocality,
Raman imaging allows for the non-­destructive and non-invasive analysis ofsuch features. The garnet was polished,leaving the inclusion intact some tens of
microns below the surface (Fig. 5A). The
Raman image (Fig. 5B) revealed significant
variations in the relative peak intensities
for the garnet across the scanned area(compare the peaks near 850 and 360 cm-1
for the red and magenta spectra in Fig. 5C).
The orange spectrum possibly represents
a carbonate phase in direct proximity to,or as part of, the inclusion. This variationis confirmed in the depth scan (Fig. 5E, F).
Changes in garnet peak intensities appeared only around the inclusion. This mayeither indicate a differential stress regime
due to the influence of the fluid inclusion,or it may be due to slight variations in thegarnet composition adjacent to the inclusion. Interestingly, the aqueous phase also
showed significant variations, as shown by
the Raman spectra (Fig. 5D, G). These variations may be attributed to the presenceof H2O in liquid and gaseous phases, or thepresence of hydrous silicate phases.

Figure 5: Fluid inclusion in garnet.

(A) Video image showing the sub-surface inclusion. The black line indicates the location of the X-Z
scan in (C). (B-D) Combined false-color Raman image (C) and corresponding Raman spectra of thegarnet and carbonate phase (C) (red, orange, pink) and of the aqueous phase (D) (green, cyan, blue).
(E-G) Combined false-color Raman image (E) for the X-Z scan along the black line in (A) and corresponding Raman spectra (F, G). Scale bars 10 µm. The spectra in (C) and (F) are normalized to the peaknear 900 cm-1.

Samples and data courtesy of Andrey Korsakov, Siberian Branch of the Russian Academy of Science,
Novosibirsk, Russia.

B

E

C

D

F

G

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In the previous example, 3D informationfrom a garnet sample was gained by recording one Raman image in the X-Y planeand one orthogonal to it in the X-Z plane.
However, an even more complete piture of
the material distribution can be obtained
from a 3D representation of the sample.
This is possible using 3D Raman imaging,where 2D images are recorded from several focal planes and a 3D representationof the sample volume is created from theimage stack.

Fig. 6 exemplarily shows the 3D Raman
image of a fluid inclusion in garnet. It
reveals the fluid water inclusion (blue)
surrounded by garnet (red), calcite (green)and mica (cyan).

Figure 6: 3D confocal Raman image of a fluidinclusion in garnet.
Water inclusion (blue) in garnet (red), calcite(green), mica (cyan).
Scan range: 60 x 60 x 30 µm3.

Asbestos fibers in mineral matrices
Asbestos refers to a group of six silicate
minerals which form fibers. Due to its
flexibility, strength and heat-resistance,
asbestos was a very popular building material. However, its use is now banned inmany countries because all asbestos forms
are highly carcinogenic. Therefore thedetection of asbestos fibers is necessary
in materials intended for construction,such as stone from quarries, and also thepreviously installed materials in old buildings. Their detection is often challenging
because the fibers’ diameters are usually
only a few hundred nanometers.
Together with the BRGM, the French national geological survey office, we recently
demonstrated the utility of combined 3D
Raman imaging and scanning electron
microscopy (SEM) for identifying andcharacterizing asbestos-like fibers in different rock samples (Wille et al. 2019). 3D
Raman measurements revealed the shapeof the fibers within the mineral matrices
and identified the chemical compositionof the fibers and the matrix. Such a 3D
analysis allows for the calculation of the
aspect ratios and volume fractions of theasbestos fibers. Fig. 7 shows actinolite
asbestos fibers (red) in an orthoclase(blue) and calcite (green) matrix (Wille etal. 2019). With an integration time of 100
ms per spectrum, the entire 3D image was
acquired in only about 2 hours.

Figure 7: Volume analysis of asbestos fibers in a mineral matrix (Wille et al. 2019).

Actinolite asbestos fibers (red) are surrounded by a matrix comprised of orthoclase(blue) and calcite (green).
Image size 60 x 60 x 20 µm3.

The measurements were performed using
a combined Raman Imaging and ScanningElectron (RISE) microscope (WITec andTescan). Thus, SEM and Raman images
could be obtained from the same sample
position, which enabled the correlation of
the structural information from SEM withthe chemical information from Raman
imaging (Wille et al. 2019).

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Topographic confocal Raman imaging with TrueSurfaceTM
TrueSurfaceTM is an optical profilometry
technology pioneered by WITec. It enables
confocal Raman microscopy on roughly
textured and tilted samples by keeping
their surfaces constantly in focus. Thus, it
is extremely useful for geological samples.
Fig. 8 illustrates topographic Raman
imaging on an inclined and rough rocksample from the Doushantuo formationin China (Fig. 8A, B). The height profile (Fig.
8C) was recorded simultaneously with theRaman spectra at each image point andrepresents the rough surface topography
in the measurement area. The topographic
Raman image (Fig. 8D) shows the chemical
information overlaid on the height profile.

B

A

C
E

D

Figure 8: Raman imaging of a rough rock(A) Photograph of the sample, a cap carbonate
rock from the Doushantuo formation (Yichang,
China). (B) White-light image of the sample. The
red rectangle marks the position of the topo­
graphic Raman measurement. (C) Height profileof the rock. (D) Topographic Raman image, inwhich topography and chemical information are
overlaid. The colors correspond to those of theRaman spectra in (E). (E) Raman spectra: red =ankerite, blue = barite, green = dolomite, pink =Al2[SO4]3, yellow = unidentified phase.

Sample courtesy of Joachim Reitner, Dept. ofGeobiology, Göttingen University, Germany.

Correlative Raman imaging: Maximizing the information gain
Due to its non-destructive and label-freenature, confocal Raman imaging is ideallysuited for correlative imaging techniques,
which greatly enhance the insight gained
from an investigation. Raman imaging
can for example be combined with various
light microscopy techniques, with atomic
force microscopy (AFM), scanning near-­field optical microscopy (SNOM) andscanning electron microscopy (SEM). Thus,
high-resolution chemical and structural
sample information can be obtained fromthe same sample area with one instrument. The efficient workflow of correlative
microscopy techniques is an additional
advantage that saves time and money.

application noteLise-Meitner-Str. 6 • D-89081 Ulm, Germany
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Raman Imaging and Scanning Electron (RISE) microscopy of a geological sample
Raman Imaging and Scanning Electron(RISE) microscopy integrates the sensitivity of the non-destructive, spectroscopic­Raman technique and the atomic resolu­
tion of scanning electron microscopy(SEM) in one instrument. Due to an intelligent and automatic sample positioning
system, RISE microscopy enables diffrac­tion-limited confocal Raman imaging and
SEM at exactly the same area of interest.
The power of RISE microscopy is illustrated
by analyzing the mineral phases of a rocksection from a drill core. The dominantrock type is diorite. The sample was nottreated or vaporized but only sectioned
with a diamond saw under water. This
reduces the risk of contaminating thesurface, which is of great importance forgeological drill cores, but also for objects
obtained from the deep sea.
Fig. 9A shows the SEM image of a small
sample area recorded using the back-scattered electron detector of the SEM. The
same area was analyzed using energy-dispersive X-ray spectroscopy (EDX/EDS)(Fig. 9B). The distribution of elementalgroups indicates the presence of three
distinct minerals. Single Raman spectra
were acquired from the three different
areas, three of which show the characteristic Raman bands for quartz, epidote
and plagioclase (Fig. 9C). This is in good
agreement with the elemental composition obtained by EDX. Raman spectra of
the three primary minerals were evaluatedusing cluster analysis. Four more spectra
were detected, two of which may corres­
pond to different grain orientations
within the epidote and plagioclase phases,
respectively. The spatial distribution of theminerals is shown in the color-coded RISE
image (Fig. 9D), in which the colors of theRaman image correspond to those of theRaman spectra (Fig 9C). In addition to thespatial distribution of the mineral phases,
small grains within a mineral phase could
be detected. Fig. 9E shows the white-lightimage acquired from the same sample

A

B

C

D

E
Figure 9: Mineral phases in a diorite rock section.

area as the SEM image. It emphasizes thathigh-resolution optical images require proper focusing, whereas SEM is completely
insensitive to surface roughness. Thus, it isdifficult to retrieve the sample area whenusing two stand-alone instruments.

(A) SEM image. (B) Overlay of SEM and EDX
images. Three element groups could be
distinguished with EDX: Si, O (orange); Ca, Fe,
Al (grey-purple); Na (green). (C) Raman single
spectra acquired from the three distinct regionswith the characteristic Raman bands of quartz(brown), epidot (red) and plagioclase (green).
(D) RISE image: Overlay of Raman and SEM
image. The colors of the Raman image correspond to those of the spectra in (C). Raman image
parameters: 100 x 100 µm2, 150 x 150 pixels= 22,500 spectra, integration time 80 ms per
spectrum. (E) White-light microscopy image ofthe same sample area.
Sample courtesy by C. Heim, Geoscience Centre
GZG, Dept. Geology, University of Göttingen,Germany.

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Raman Imaging and Scanning Electron (RISE) microscopy of hematite
A piece of hematite (Fe2O3) was analyzed by SEM and thenwith the integrated confocal Raman microscopy functionof the RISE microscope. SEM reveals structural characteristics, but cannot differentiate between the different oxides
present in the hematite. However, the Raman spectra
indicate the occurrence of several crystal forms of hematite and of goethite (FeO(OH)). The distribution of these minerals is shown in the Raman image that has been overlaid
onto the SEM image (Fig. 10).
Figure 10: Raman-SEM image of hematite.

The sample consists of several crystal forms of hematite (red, blue,
green, orange, pink) and of goethite (light blue, cyan). The Raman
image was overlaid onto the SEM image.
Raman image parameters: 50 x 50 μm2; 150 x 150 spectra, integra­
tion time: 150 ms/spectrum, 10 mW laser power.

Atomic force microscopy of fossils
Atomic force microscopy (AFM) is a
non-destructive imaging technique forsurface characterization on the nanometerscale. In addition to high-resolution topography images, local material properties
such as adhesion or stiffness can be investigated by analyzing the tip-sample interaction forces. Fig. 11 shows AFM images ofsilicified bacteria. Cellular structures can‘tbe distinguished in the topography image(Fig. 11A), but are revealed in the image ofdifferent adhesion levels (Fig. 11B).
AFM is combinable with confocal Raman
imaging in one instrument. Thus, AFM
and Raman images can be obtained fromthe same sample area, making it possible
to correlate the structural and chemical
information.

A

B

References
Rotundi A. et al. (2008) Meteoritics and Planetary Science 43: 367-397. DOI: 10.1111/j.19455100.2008.tb00628.x
Steele A. et al. (2007) Meteoritics and Planetary
Science 42: 1549-1566.
DOI: 10.1111/j.1945-5100.2007.tb00590.x
Toporski J. et al. (2004) Sweeping the skies:
Stardust and the origin of our Solar System.
Imaging & Microscopy 04/2004: 38-40.
Wille G. et al. (2019) Journal of Hazardous Materials 374: 447-458.
DOI: 10.1016/j.jhazmat.2019.04.012

Further reading
Confocal Raman Microscopy, Toporski J., Dieing
T. and Hollricher O. (eds.). Springer Series in
Surface Sciences 66, Springer International
Publishing AG, 2nd ed. (2018).
DOI: 10.1007/978-3-319-75380-5
Figure 11: AFM images of silicified bacteria.

(A) Topography AFM image. Cell structures can not be recognized from the topography. (B) The AFM
image recorded in Digital Pulsed Force Mode shows the different adhesion levels and reveals the cellstructures of the bacteria. Scale bars 1 µm.

WITec Microscope Seriesalpha300 S: Scanning
Near-field Optical Microscopealpha300 A:
Atomic Force Microscopealpha300 R:
Confocal Raman Microscopealpha300 apyron: AutomatedConfocal Raman Microscope

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